NSUF - Nuclear Science User Facilities

Radiation tolerance of Ln3TaO7 weberite-type nuclear waste matrix materials

Full Details
Principal Investigator
Name:
Rodney Ewing
Email:
[email protected]
Phone:
(208) 526-6918
Team Members:
Name: Institution: Expertise: Status:
Boopathy Kombaiah
Mukesh Bachhav
Osman Anderoglu
Chien-Hung Chen Stanford University TEM / microstructural analysis Post Doc
Yue Xia Stanford University Sample preparing, TEM performing Graduate Student
Experiment Details:
Experiment Title:
Radiation tolerance of Ln3TaO7 weberite-type nuclear waste matrix materials)
Work Description:
To investigate, at an atomic level, the radiation tolerance and structural evolution of Ln3TaO7 weberite-type structures under irradiation, in situ 1 MeV Kr irradiation will be performed on several compositions using the Intermediate Voltage Electron Microscopy (IVEM)-Tandem facility at Argonne National Laboratory. A constant ion flux of 6 × 1011 ions/cm2/s will be used to minimize irradiation-induced temperature changes during the experiments. Specimens (polished pellet mounted on Cu TEM grid) will be bombarded by the ion beam at an angle 30° off the electron beam direction. During the irradiation, the electron beam will be blocked to avoid concurrent electron beam irradiation damage. We propose systematic experimental studies of the role of composition (Ln = Sm, Y, Eu, Gd, Lu) and temperature (200 K, RT, 450 K, 600 K) on the radiation response of these compounds. The irradiation-induced structural evolution will be characterized by in situ TEM imaging and selected area electron diffraction (SAED) patterns at various ion fluences (dose up to 30 dpa).
Project Summary
In this project, 1 MeV Kr ions will be used to irradiate Sm3TaO7, Y3TaO7, Eu3TaO7, Gd3TaO7 and Lu3TaO7 (up to 30 dpa) at 200 K, RT, 450 K, and 600 K to study the radiation tolerance and structural evolution in these nuclear waste form matrix materials. DF/BF images and SAED patterns will be collected at various fluences to observe the structural modifications induced, as well as the specific temperatures and ion fluences at which these modifications occur. In addition, ion irradiation-induced microstructural evolution, including defect evolution and phase transformations, will be compared among these weberite-type compounds.



This project needs one-week of observation time at the IVEM facility. We anticipate observing the formation and evolution of defects, including point defects, dislocation loops, and stack faults, as well as phase transformation processes, as a function of fluence and temperature. By comparing the radiation responses of these compounds, we will obtain insight into the manner in which temperature and composition affect the radiation tolerance of weberite-type phases, thus helping to design radiation tolerant materials in this system for next generation nuclear waste matrices.

Relevance
The Office of Used Nuclear Fuel Disposition Research and Development (UNFD R&D) is investigating various geologic media and concepts for the disposal of spent nuclear fuel (SNF) and HLW that exists today and that will be generated under future fuel cycles. For long-term disposition, the performance and safety of the nuclear waste form, which immobilizes waste within a geologic repository, is a critical aspect of the back-end of the nuclear fuel cycle. Ln3TaO7 weberite compounds are promising candidates for providing reliable and stable long-term immobilization, as they combine high radionuclide incorporation with exceptional stability under irradiation (often superior to previously-studied complex oxide waste forms).In this project, study of the atomic structure evolution and radiation tolerance of Ln3TaO7 weberite-type compounds in simulated disposal environments will contribute to understanding of the mechanisms of radiation damage in this and related complex oxide waste forms, and will further promote the development of HLW form matrix materials. Characterization of the compositional variation in radiation tolerance will contribute to the design of improved immobilized materials with superior properties and performance.

About Us

The Nuclear Science User Facilities (NSUF) is the U.S. Department of Energy Office of Nuclear Energy's only designated nuclear energy user facility. Through peer-reviewed proposal processes, the NSUF provides researchers access to neutron, ion, and gamma irradiations, post-irradiation examination and beamline capabilities at Idaho National Laboratory and a diverse mix of university, national laboratory and industry partner institutions.

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